RFR: JDK-8285764: Add system property for Java SE specification maintenance version

[Joe Darcy]

Add a new system property, java.specification.maintenance.version, to return the maintenance release number of the Java SE specification being implemented. The property is unset, optional in the terminology of System.getProperties, for an initial release of a specification.

Please also review the CSR https://bugs.openjdk.java.net/browse/JDK-8285764

I'll update copyright years before an integration.

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Commit messages:
 - Update comment in template.
 - JDK-8285497: Add system property for Java SE specification maintenance version

Changes: https://git.openjdk.java.net/jdk/pull/8437/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8437&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8285764
  Stats: 7 lines in 2 files changed: 7 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8437.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8437/head:pull/8437

PR: https://git.openjdk.java.net/jdk/pull/8437